Mini Facotry Reset option disabled on Kobo Mini

Hi,

I just got a second hand Kobo Mini. It appears to be working well, except for one problem -- I can't perform factory reset.

The manual suggests only one option -- go to Settings, Device Information, and tap FACTORY RESET button. However, FACTORY RESET button on my device is greyed out.

I have tried fully charging the device, and performing the basic reset, but Factory Reset button remains greyed out.

Software version is 2.1.5 (r43939, 10/12/12).

Any suggestions?

Cheers,
Harvey